Solar Rays

Ultraviolet (UV) radiation is the part of the invisible radiation spectrum created by the sun. UV radiation is made up of elementary particles known as photons, which are categorised into wavelengths. The wavelength varies inversely in accordance to its energy – the shorter the wavelength, the greater its energy. The skin reflects some UV radiation naturally, but care must be taken since that which penetrates the skin tends to damage the cells permanently.

There are three types of UV rays: UVA, UVB and UVC. The UV radiation wavelength range is 100-400nm, often referred to as the Broad Spectrum. These levels are not constant and are subject to change from seasons, atmosphere and even the time of day.

UVA

UVA accounts for the largest amount of UV radiation to reach the Earth’s surface and accounts for 10% of all solar rays – 90% of UV energy received by unprotected skin comes from teh UVA range (Osterwalder et al).Although lower in energy than UVB, it is believed that UVA causes damage to the connective tissue and increases the chances of skin cancer. 80% of UVA rays penetrate to the dermal layer of the skin and a further 20% penetrate even further.

UVA radiation can travel through clear glass and is mainly responsible for the ageing effect, causing wrinkling of the skin.

UVB wavelength range: 280 – 320nm

There is less UVB radiation reaching the Earth’s surface than UVA since large portions are absorbed by the ozone layer.

UVB radiation is higher in energy but does not penetrate the skin as far as UVA radiation. The horny layer of the skin reflects 70% of UVB radiation. The remaining 30% infiltrates as far as the epidermal layer, where some is absorbed by keratinocytes and melanin. 10% of UVB radiation reaches as far as the dermal layer.

Although UVB radiation does not penetrate the skin as deep as UVA radiation, it has a higher energy level that makes it very active, therefore causing damage to the skin. This damage is not as visible but takes effect within seconds of exposure and results in sunburn.

UVC wavelength range: 100 – 280nm

UVC radiation is absorbed by the ozone layer and does not reach the earth’s surface. UVC radiation is extremely dangerous for humans; some forms are produced on the Earth’s surface by such processes as arc welding.

Infrared Radiation wavelength range: 800 – 3200nm

About 50% of the solar rays that reach the Earth’s surface are infrared rays. These are the solar rays that are responsible for warming the skin and body.

Visible Light wavelength range: 400 – 800nm

About 40% of the rays that reach Earth’s surface are visible light rays, unless they are blocked by the elements. Visible light travels through the skin.